CorebootModulePkg/CbSupportDxe: Add EFIAPI to CbDxeEntryPoint

All image entry point functions must use EFIAPI.

Some GCC toolchains will have a build error without this fix.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Scott Duplichan <scott@notabs.org>
---

Index: CorebootModulePkg/CbSupportDxe/CbSupportDxe.c
===================================================================
--- CorebootModulePkg/CbSupportDxe/CbSupportDxe.c	(revision 17108)
+++ CorebootModulePkg/CbSupportDxe/CbSupportDxe.c	(working copy)
@@ -122,6 +122,7 @@
 
 **/
 EFI_STATUS
+EFIAPI
 CbDxeEntryPoint (
   IN EFI_HANDLE         ImageHandle,
   IN EFI_SYSTEM_TABLE   *SystemTable